The present invention relates to a power window device for automatically lowering and raising a window member by operating a switch.
In the prior art, a power window device is installed in a door of a vehicle to facilitate the lowering and raising of a window glass (opening and closing of a window) in the door. The power window device includes a window switch, which is arranged in a passenger compartment (e.g., inner side of the door) and operated by a vehicle occupant. Operation of the window switch drives a drive motor, such as a DC motor, so as to automatically lower or raise the window glass. When the window switch is operated to open the window, the drive motor produces normal rotation and lowers the window glass. When the window switch is operated to close the window, the drive motor produces reverse rotation and raises the window glass.
FIG. 4 is a block diagram showing one example of a power window device 51. The power window device 51 includes a plurality of drive units 52 to 55 for lowering and raising associated window glasses. In this example, there are four drive units 52 to 55, one for a driver door, one for a front passenger door, one for a rear right door, and one for a rear left door. The drive units 52 to 55 respectively include electronic control units (ECUs) 56 to 59. Each of the drive units 52 to 55 further includes a window switch 61 and a drive motor 60. The window switch 61 is operated to drive the drive motor 60 and lower or raise the window glass accordingly.
The driver door ECU 56 functions as a master ECU for the front passenger door ECU 57, the rear right door ECU 58, and the rear left door ECU 59 to validate and invalidate operation of the ECUs 57 to 59. A driver uses an engine switch to start the engine. When the engine starts to run, the engine switch is shifted to an ignition (IG) position. The driver door ECU 56 monitors the engine switch. When determining that the ignition switch is located at the IG position, the driver door ECU 56 cyclically transmits a validation signal Sr to the ECUs 57 to 59 through a signal path, or signal wire 62. Control of the ECUs 57 to 59 over the drive motors 60 is validated when the ECUs 57 to 59 receive the validation signal Sr. Conversely, when determining that the engine switch is not located at the IG position and the engine is thus not running, the driver door ECU 56 cyclically transmits an invalidation signal Sy to the ECUs 57 to 59 through the signal path, or signal wire 62. Control of the ECUs 57 to 59 over the drive motors 60 is invalidated when receiving the invalidation signal Sy. In this state, the corresponding window glass cannot be lowered and raised even if the window switch 61 is operated.
Current may leak from the signal wire 62 when the power window device 51 is exposed to moisture. In other cases, the signal wire 62 may be broken when a short circuit occurs. Under such circumstances, the signal wire 62 is substantially in an unexpected condition. Thus, the driver door ECU 56 cannot properly communicate with the ECUs 57 to 59, which function as slaves. The slave ECUs 57 to 59 are each provided with a function for detecting such a state in which the signal wire 62 is in an unexpected condition (refer to, for example, Japanese Laid-Open Patent Publication No. 2004-312957). When the signal wire 62 is determined as being in an unexpected condition, further operation of each of the ECUs 57 to 59 is invalidated.
In this manner, by invalidating control of the ECUs 57 to 59, the window glasses are not erroneously operated. However, the driver door ECU 56 is directly connected to the ignition switch IG. Thus, even if the signal wire 62 is in an unexpected condition, control of the driver door ECU 56 is continuously enabled.
However, problems may occur if the power window device 51 cannot be operated from the front passenger seat and the left and rear right passenger seats when the signal wire 62 is in an unexpected condition. For example, if the signal wire 62 is in an unexpected condition in a state in which the window is open, the window cannot be closed from the front passenger seat and the left and rear right passenger seats when it starts to rain. Further, if the vehicle becomes submerged in water and the signal wire 62 is in an unexpected condition, the power window device 51 would not operate when a vehicle occupant tries to open a window from the front passenger seat, the rear left passenger seat, or the rear right passenger seat. This would not be desirable in a state of emergency.